Particle studying device control circuit



United States Patent O 3,271,672 PARTICLE STUDYING DEVICE CONTROLCIRCUIT Michael I. Henderson, London, England, assignor to CoulterElectronics, Inc., Chicago, Ill.

Continuation of application Ser. No. 139,516, Sept. 20, 1961. Thisapplication Oct. 4, 1965, Ser. No. 492,732 21 Claims. (Cl. 324-71) Thisapplication is a continuation of application Serial No. 139,516, tiledSeptember 20, 1961, now abandoned.

This invention relates generally to a particle analyzing device used instudying the physica-l properties of particles suspended in a fluid, andmore particularly is concerned with -an improvement in the analyzingdevice control cir cuit disclosed and claimed Iby Wallace H. Coulter inU.S. Patent application, Serial No. 101,289 filed April 6, 1961, nowabandoned.

Reference may be had to the Coulter patent application for the detailsof the structure upon which this invention comprises an improvement.

Reference may also be had to U.S. Patent No. 2,656,- 508 to Wallace H.Coulter and U.S. Patent No. 2,869,078 to Wallace H. Coulter and JosephR. Coulter, Ir., which describe the basic principles and structures usedin scanning particles suspended in a fluid, by one of the Coultermethods.

Small particles, such as blood cells, food and fat particles, libres,plastics, dusts, catalysts, metals and the like are counted and sized inmany modern laboratories, factories and institutions throughout the`world by `means of the apparatus of the patents referred tohereinabove. According to one of the Coulter methods a suspension ispre-pared of the particles to be studied in a fluid such as a liquidelectrolyte whose resistivity is different than that of the particle.The suspension is drawn through a scanning aperture immersed in thesuspension, and each time a suspended particle passes through theaperture, the resistivity of the liquid path within the aperture changesdetectably by an amount which is a direct function of the volume ofliq-uid displaced by the particle in the aperture.,

A direct current is caused to ow through the liquid path in the scanningapert-ure, and the momentary chan-ge in resistivity is manifested in asignal pulse which appears across a pair of scanning electrodes,respectively located on opposite sides of the -aperture in the liquid.In the preferred embodiment, the aperture is located in the side wall ofa glass tube which is immersed in the liquod suspension contained in aglass beaker. The interior of the tube is hydraulically connected -to aclosed liuid system which may comprise a mercury manometer. Thedunctions of the mercury manometer are to cause the liquid to be drawnthrough the scanning aperture and to generate signals indicating thebeginning and the end of an analytic run, in the period during which anaccurately metered volume of liquid is scanned.

The sign-al pulses which appear across the two scanner electrodes areamplified and analyzed in a multi-stage electronic circuit in order tocount the number of particles having a desired characteristic, toseparate signals representing particles of different sizes, and toperform other types of analyses.

Users of structures embodying the principles of the prior art recognizedthat several problems existed with respect to continuous electriccurrent flow in the scanning aperture and switching transients whichcaused erroneous results. Because the dimens-ions of the aperture are onthe order of several to 100 microns in size, a small current iowing inthe scanning electrode circuit causes a high current density in the`aperture which in turn causes the boiling of the liquid in the aperturewhen ythe liuid flow ceases at the end of an analytic run. Biologicalparticles,

Patented Sept. 6, 1966 lCe such as blood cells, food particles andbacteria, which come to rest within the apert-ure under staticconditions, that is when the fluid suspension is not flowing, willexpand or burst due -to the boiling of the liquid within the vapertureand become debris. It has 'been realized, therefore, that means must beutilized to de-energize the scanning electrode circuit when -the liuidflow through the aperture ceases.

It also has been realized that the deleterious effects of spurious inputsignals must be prevented by incorporating means for activating theanalyzer circuit of the particle studying device only during the periodof lan analytic run.

In the above referred to Coulter application, these programmingfunctions were regulated lby a complex control circuit comprising aflip-dop circuit having two tubes and other associated components. Theflip-flop circuit had two states and its was necessary to provideconnections so that the liip-liop could be switched from one state tothe other in order to accomplish the desired results.

The primary object o-f the invention herein is to provide a highlysimplified structure which automatically controls the energization ofthe scanning electrode circuit and the operation of the electroniccircuits which analyze the signals generated by the scanning electrodecircuit.

Other objects of the invention will appear from the followingdescription of a preferred embodiment of the invention.

In the drawing:

FIG. 1 is a simplified block diagram of a preferred embodiment of aparticle studying device with which the invention herein is associated.

FIG. 2 -is a circuit diagram of the invention as incorporated in aCoulter-type'particle studying device.

Basically the novel structure of the invention comprises an additionalstop electrode in the metering section of the manometer and associatednovel circuitry for programming the operation of the scanner electrode,and analyzer circuits before, during and after the period of ananalytric run.

In FIG. 1 t-he block which is marked Stand comprises both the signalgenerating scanning elements and the metering device of the basicapparatus. The commercial version of the apparatus has all of thestructure mounted on a single standard; hence, this has come to be knownin the art as the stand In the preferred embodiment to be described, theprogram sequences are synchronized to the beginning and the end of theperiod of an analytic run by signals which are generated by the movementof the tail of a mercury column in a manometer, past sensing pointslocated on a metering section of the manometer tube.

The scanning signals, 4generated by the scanning element of the stand inthe manner described in the patents, are transmitted to a preamplifierby channel 10. The preamplier transmits the amplified scanning signalsto a main amplifier by way of channel l12. The main amplitier furtherincreases the level of the scanning signals and transmits these signalsto the input of a threshold detector circuit via channel 14 and to thevertical deflection amplifier input of a cathode ray oscilloscope viachannel 15.

Basically, the threshold detector circuit discriminates between signalsWhose amplitudes exceed a threshold level and signals whose amplitudesdo not exceed that threshold level. In this embodiment, only thoseportions of the signal pulses having heights in excess of the thresholdlevel will appear at the output on channels 16 and 30. Since theamplitudes of the pulses which occur as the result of the scanning ofparticles through the aperture are generally directly porportional tothe volume of their respective particles, the particles may be sized 3by varying the threshold level and recording the number of pulsesappearang at the threshold detector circuit output.

The functions of the oscilloscope are to display visually the pulseswhich are amplified by the preamplifier and the main amplifier upon theface of the cathode ray tube and to identify the portions of the pulseenvelopes having heights in excess of the threshold level.

The beam intensity circuit of the cathode ray oscilloscope is connectedto an output of the threshold detector circuit by channel 30 in order toaccomplish the second function.

Channel 16 is connected to the input of an implifier and gate circuit.This circuit performs the dual functions of acting as a signal gate inresponse to a program signal received from start channel 48 and ofgener-ating a count pulse in response to a signal pulse received fromchannel 16 when gated open in response to a program signal. In thisembodiment, the start channel 48 is connected between a manometer startelectrode and the amplifier and gate so that when the start electrode isnot grounded by the mercury manometer column, the amplifier and gate isclosed. When the electrode is grounded, as when the mercury of themanometer engages the electrode, the amplifier and gate will commence totransmit signals via channel 18 to a counter.

The stop circuit is activated or caused to become operative through theengagement of the tail of the mercury column of the manometer with apair of stop electrodes provided at the downstream end of `the meteringsection. The grounding of the first electrode, STOP (1), by the`grounded mercury column serves to bias off, de-activate or otherwisedisable one or more of the stages of the analyzing circuit; therebypreventing spurious signals from being transmitted through the circuits.In the particular apparatus shown, a channel 112 for transmitting aclisabling signal extends to the preamplifier, but as shown by thebroken line connections 112', 112" and 112'", the stop circuit mayinstead or in addition be connected to the main amplifier or any otherconvenient following stage.

In FIG. 2, there is illustrated a circuit diagram of the stand,preamplifier and stop circuit portions of the particle studying deviceillustrated in block diagram form in FIG. 1.

The reference character 60 is used generally to designate the manometeror program signal source while the reference character 62 is usedgenerally to designate the scanning signal source. The scanning signalsource 62 is formed of a first vessel 64 of insulating material whichhas a scanning electrode 66 immersed in a suspension 70 which is to betested. A second insulated vessel 68 in the form of a small diametertube, having an electrode 74 in its interior, is immersed in thesuspension 70 so that a microscopic aperture 72 provided in the sidewall of the tube 68 is below t-he surface of the suspension.

This aperture and the circuit containing electrodes 66 and 74 comprisethe scanning means. Each time a particle passes through the aperturethere will be a change in the resistance of the electric current pathcomprising the volume of suspension included within the aperture, whichis detectable `by the analyzing circuit. The second electrode 74,mounted on the interior of the tube 68, is connected to ground 96 by wayof lead 76. The electrode 66 is connected to terminal 78 which is theinput terminal of the preamplifier circuit.

It will be noted that the tube 68 is in a closed liuid system, the upperend of which is provided with a valve 80 that leads to a source ofvacuum and an upper branch 82 which leads to the manometer 60. Themanometer 60 has a column of mercury 84 which is shown in the drawing inan unbalanced condition. The tubing of the manometer is of capillarydimension although shown exaggerated in size for clarity. A mercuryreservoir is shown at 86 and there is a relatively horizontal meter- 4ing section at 88 within which a start electrode 90 and stop electrodes91 and 92 are located. An electrode 94, for applying to the mercurycolumn a reference potential which is common to the circuits controlledby the electrodes 90, 91 and 92, is connected to reference ground 96 byway of a suitable conductor.

There is a direct electric current which is normally owing through theaperture 72 at the same time that the fiuid suspension is passingthrough the aperture. This current follows the path which extends fromthe +240 volt D.C. source which is connected to a bus 100, by way ofrheostat R-3 to the terminal 78. From the terminal 78 the current flowsby way of connection 102 through the suspension 70 to ground by way ofthe electrodes 66 and 74 and the connection 76. When a particle passesthrough the aperture 72, there will be a signal in the form of a voltagepulse appearing at the terminal 78 and this will be applied throughcoupling condenser C-2 to the grid of triode V-8A of the preamplifier.

The preamplifier is designated generally 104 and as will be seen, itcomprises triodes V-SA and V-SB which are connected to amplify thescanning signal. The scanning signal which is applied to the grid of thetriode VSA is amplified in that triode and applied by way of aconventional coupling network through condenser C3 which is connectedbetween the plate of triode V-8A and the grid of the triode V-8B.

The triode V-SA is biased in a conventional manner through the use of agrid leak resistor R-19 and a cathode resistor R-21. The triode V-SBhas, in addition to a grid leak resistor R-22 and a cathode resistorR-24, a second grid resistor R-23 to control the bias of the grid in amanner to enable the triode V-SB to be readily biased off, as will beexplained.

Signals which are generated by the scanning signal source 62 will appearacross the plate load of the triode V-SB comprising gain controlpotentiometer RV-12, capacitor C-S and the output circuit, only if bothof the triodes V-SA and V-SB are conducting. It will be noted that thereis a voltage divider which comprises resistors R-17, R-18 and R-11connected in series from the +240 volt D.C. bus 100 to the -275 volt DC. bus 108. There is a diode V-7 which is connected between the junctionof resistors R-22 and R-23 and the junction of resistors R-18 and R-11.When the stop electrode 91 is not grounded by the mercury column, thejunction of resistors R-17 and R-18 and lead 115, and the junction ofresistor R-18 and diode V-7 are at positive potentials. The diode V-7 isback biased, thereby isolating the voltage divider from the grid biasnetwork of the triode V-8B. The triode V-SB is biased for conductionbecause of the choice of values for resistors R-22, R-23 `and R-24. Whenthe stop electrode 91 is grounded, the potential at the cathode of diodeV-7 becomes negative, thereby causing the diode to conduct and the biasvoltage onthe triode V-SB to drop below the triodes cut-off biasvoltage.

To initiate an analytic run, the Valve 80 is opened and the mercury inthe manometer unbalanced to the condition shown. After resetting thecounter, the valve is closed and the mercury from the reservoir 86 willnow fall to its equilibrium level thereby creating a pressuredifferential between the inside and the outside of the aperture tube 68which causes the fluid 70 to be drawn through the aperture 72.

As the amplifier and gate circuit remain biased off, no signals aretransmitted to the counter. After the tail of the mercury column passesup bend 132 and engages the electrode 90, a circuit is completed fromground 96 through the common electrode 94 through the mercury column tothe start electrode and by way of start channel 48 to the amplifier andgate to open the gate so that pulses may be transmitted to the counter.As the merury column moves toward equilibrium, the suspension 70 isdrawn through the aperture 5. 72. The scanning signals which aregenerated appear across the electrodes 74 and 66 may pass through theapparatus and may be counted.

The counting continues during the period of the analytic run until thetail of the mercury column traverses the entire metering section 83 andengages the rst stop electrode 91. When this occurs, the junction of theresistors R-l7 and R-IS is placed at ground potential; thereby causingtriode V-SB to be biased to cut,- off as described above. No signalswill pass through the triode V-B thereafter. Immediately after thisoccurs, the tail of the mercury column reaches the sec ond stopelectrode 92 and establishes a circuit from the conductor 76 through theground 96 to the common electrode 94, through the mercury column to theelectrode 92, by way of the conductor 114 to the electrode 66, therebyplacing a direct short circuit across the electrodes 66 and 74 andpreventing any further flow of current through the liquid path in theaperture.

In the patent application which has been referred to above, a start-stopHip-flop circuit was used to perform the function of disabling a stagefollowing the input terminal 78 while also cutting off the ow of currentto the aperture. Since the flip-flop is a two-state device, it wasnecessary to provide a circuit for changing the flip-flop from one stateto the other. Such a provision is unnecessary in the circuit of thisinvention as the structure of the metering section comprising the threeelectrodes and the grounded mercury column serves as the memory for theprogram circuit.

The heart of the structural novelty lies `in the use of the thirdelectrode 92. Unlike the metering apparatus taught in U.S. Patent No.2,869,078 which contains only one start electrode and one stopelectrode, the metering structure of this invention allows theindependent programming of scanner electrodes and the analyzer circuitswithout the need for an external memory or isolation circuit such as aflip-flop. Further the circuit of the invention is fully automatic foras soon as Huid llow is restored in the aperture 72, the pressuredifferential within the closed fluid system causes the tail of themercury column to withdraw above the electrode 92, thereby restore thescanning electrode current. No memory or reset switch is necessary;therefore a more reliable circuit having a lower cost is readilyachieved.

What it is desired to secure by Letters Patent in the United States is:

1. A particle analyzer, for studying particles suspended in a fluid,comprising:

(a) fluid suspended particle scanning means, having a pair of scannerelectrodes, for generating scanning signals, each signal having aparameter which is a function of a physical property of a respectivescanned particle;

(b) means for analyzing the scanning signals;

(c) liquid manometer means for metering the volume of fluid scanned,having a metering section;

(d) means for sensing the passage of the manometer liquid past a firstpoint in the metering section and for generating a rst program signal;

(e) means for sensing the passage of the manometer liquid past a secondpoint in the metering section and for generating a second programsignal;

(f) means for sensing the passage of the manometer liquid past a thirdpoint in the metering section and for generating a third program signal;

(g.) means for activating the analyzing means in response to the receiptof the first program signal;

(h) means for de-activatingthe analyzing means in response to thereceipt of the second program signal; andl (i) means for de-energizingthe scanning means in response to the receipt of the third programsignal;

the rst point being separated from the other points by a distance whichis a function of the volumeV of fluid scanned during the period of ananalytic run, whereby the analyzing means are activated only during theperiod of an analytic run and the scanning means are dce-energized afteran analytic run.

2. The combination recited in claim 1 wherein the sensing means generateprogram signals in response to the passage of the tail of the manometerliquid past their respective points.

3. The combination recited in claim 1 whereinthe manometer liquid iselectrically conductive and the sensing means comprise electrodes havingportions within the interior of the metering lsection whereby they maycontact the manometer liquid.

4. The combination of claim 1 `wherein the first sensing means areupstream of the other sensing means.

5. The combination recited in claim 1 wherein the second sensing meansare upstream of the third sensing means.

6. The combination recited in claim 3 wherein the means forde-energizing the scanning means incorporate means for short circuitingthe pair of scanner electrodes comprising:

(a) means Jfor maintaining one of the scanner electrodes and themanometer liquid -at the same potential; and

(b) means for maintaining the third sensing electrode and the otherscanner electrode at the same potential whereby passage of the manometerliquid past the third sensing electrode causes both scanner electrodesto be maintained `at the same potential.

7. A particle analyzing device, for studying particles suspended in afluid, comprising:

(a) fluid suspended particle scanning means, having a pair of scannerelectrodes for generating scanning signals, each signal having aparameter which is a function of a physical property of a respectivescanned particle;

(b) means for `analyzing the scanning signals;

(c) liquid mercury manometer means for metering the volume of fluidscanned, having a metering section;

(d) means for applying a potential to the mercury in the manometer;

(e) a rst electrode` located at .a rst point on the metering section andhaving a portion of its surface within the interior of the meteringsection;

(f) `a second elect-rode located `at a second point `on the meteringsection and having a portion of its surface within the interior of themetering section;

(g) a third electrode located at a third point on the metering sectionand having a portion of its surface within the interior of the meteringsection;

(h) means for activating the analyzing means when la rst terminal isconstrained. to the same potential as that applied to the mercury in themanometer;

(i) means for de-activating the analyzing means when a second terminalis constrained to the same potential as that applied to the mercury inthe manometer;

(j) means for maintaining one of the scanner electrodes at the samepotential as that applied to the mercury in the manometer;

(k) means for maintaining the third electrode `and the otherscannerelectrode at the same potential;

(l) a rst conductor connecting the first electrode to the firstterminal; and

(rn) .-a second conductor connecting the second electrode to the secondterminal.

8. In a particle analyzer for studying particles suspended in a fluidhaving lluid suspended particles scanning means, incorporating a pair ofscanner` electrodes, for generating scanning signals, each signal havinga parameter which is a function of a physical property of a respectivescanned particle; `and means for analyzing the scanning signals, aparticle analyzer control system comprising:

(a) liquid manometer means for metering the volume of fluid scanned,having a metering section;

(b) means for sensing the passage of the manometer liquid past a rstpoint in the metering section and for generating a rst program signal;

(c) means for sensing the passage of the manometer liquid past a secondpoint in the metering section and for generating a second programsignal;

(d) means for sensing the passage of the manometer liquid past a thirdpoint in the metering .section and for generating a third programsignal;

(e) means for activating the analyzing means in response to the receiptof the lirst program signal;

(f) means for de-activating the analyzing means in response to thereceipt of the second program signal; and

(g) means for de-energizing the scanning means in rc- `sponse to thereceipt of the third program signal,

the rst point being separated from the other points by a distance -whichis a function of the volume of uid scanned during the period of ananalytic run, whereby the analyzing means are activated only `during theperiod of an analytic run and the scanning means are de-energized after`an lanalytic run.

9. The combination recited in claim 8 wherein the sensing means generateprogram signals in response to the passage of the tail of the manometerliquid past their respective points.

1). The combination recited in claim 8 wherein the manometer liquid iselectrically conductive and the sensing means comprise electrodes havingportions within the interior of the metering section whereby they maycontact the manometer liquid.

11. The combination of claim 8 wherein the first sensing means areupstream of the other sensing means.

12. The combination recited in claim 8 wherein the second sensing meansare upstream of the third sens-ing means.

13. The combination recited in claim 10 wherein the means forde-energizing the scanning means incorporate means for short circuitingthe pair of scanner electrodes comprising:

(a) means for maintain-ing one `of the scanner electrodes and themanometer liquid at the same potential; and

(b) means for maintaining the third sensing elect-rode whereby passageof the manometer liquid past the third sensing electrode causes -bothscanner electrodes to -be maintained at the same potential.

14. `In a particle analyzer `for studying particles suspended in Aafluid having uid suspended particle scanning means, incorporating a pair.of scanner electrodes, for generating scanning signals, each signalhaving a parameter whi-ch is a function `of a physical property of arespective scanned particle; and means for analyzing the scanningsignals, a particle analyzer control system comprising:

(a) liquid mercury manometer means for metering the volume of fluidscanned, having `a metering section;

(-b) means yfor applying a potential to the mercury in the manometer;

(c) la Kiirst electrode located at a lrst point on the metering sectionand havin-g a portion of its surface within the interior `of .themetering section;

(d) a second electrode located at a second point on the metering sectionand Ihaving a portion of its surface within the interior of the meteringsection;

(e) a third electrode located `at a third point on the metering sectionand having Ia portion of its surface within the interior of the meteringsection;

(t) means for activating the analyzing means when a rst terminal isconstrained to the same potential as that applied to `the mercury in themanometer;

g) means for tie-activating the analyzing means when a second terminalis constrained to the same potential as that applied to the mercury inthe manometer;

(h) means for maintaining one of the scanner electrodes at the ysamepotential `as that applied to the mercury in the manometer; and

(i) means `for maintaining the third electrode and the other scannerelectrode at the same potential.

15. A fluid metering device, for metering a volume of fluid suspension-containing particles which are scanned during `a period of an analyticrun by a particle analyzer incorporating means for activating theanalyzer upon receipt of a first program signal, means for de-activatingthe analyzer upon receipt of a second program signal, means `for.scanning particles `having a pair of scanning electrodes and means `forde-energizing the scanning electrodes upon receipt of a third programsignal, comprising:

(a) means for separating two bodies of iluid suspension having ascanning aperture through which a volume of uid suspension may pass whena uid pressure differential exists yacross the aperture; and

(b) manometer means for causing a pressure differential to exist acrossthe Iaperture and for metering the volume of uid passing through theaperture incorporating (i) a manometer tube having a metering section inuid connection with the aperture,

(ii) a manometer Iliquid within the tube,

(iii) means for sensing the movement of the manometer liquid past aiirst point: in the metering section and for generating the iirstprogram signal in response to this event,

(iv) means for sensing the movement of the manometer liquid past asecond point in the metering section and for generating the secondprogram signal in response to this event, and

(v) means for sensing the movement of the manometer liquid past a thirdpoint in the metering section and for generating the third programsignal in response to this event;

the first being separated `from the other points by a distance which isa function of the volume of the fluid suspension which is `scannedduring the period of an analytic run.

16. The combination recited in claim 15 wherein the .sensing meansgenerate program signals in response to the .passa-ge of the tail of themanometer liquid past their respective points.

17. The `combination Irecited in claim 15 wherein the manometer liquidis electrically conductive and the sensing ymeans comprise electrodeshaving portions within the interior 4of the metering section wherebythey may contact the manometer liquid.

18. The combination of claim 15 wherein the iirst sensing means .areupstream of the other sensing means.

19. The combination recited in claim 15 wherein 'the second sensingmeans are upstream of the third sensing means.

20. The combination recited in claim 17 wherein the means forde-energizing the scanning means incorporate means for short -circuitingthe pair of scanner electrodes comprising:

(a) means for maintaining one of the scanner electrodes and themanometer liquid at the same potential; and

(b) means for maintaining the third sensing electrode and the otherscanner electrode at the same potential whereby passage of them-anometer liquid past the third sensing electrode causes both scannerelectrodes to be maintained at the same potential.

21. A fluid metering device, for metering a volume of Huid suspensioncontaining particles which are scanned during a period of an analyticrun iby a particle analyzer incorporating means `for scanning particleshaving a pair of scanning electrodes, means for `activating the analyzerwhen a rst terminal is constrained to a reference potential and meansfor de-activating the analyzer when a second terminal is constrained tothe reference potential, comprising:

(a) means for separating two bodies of uid suspension having a scanningaperture through which a volume of fluid suspension may pass;

(b) la manometer tube having a metering section in ilu-id connectionwith the aperture;

(-c) a liquid mercury column within the manometer tube;

(d) means for applying the reference potential to the mercury column andone of the scanning electrodes;

(e) 4a rst electrode located at .a iirst point on the metering sectionand having a .portion of its surface Within the interior of the meteringsection;

(f) a second electrode located at a second point on the metering sectionan-d having a portion of its surface within the interior `of themetering section;

(g) a third electrode located at -a third point on the metering sectionand having a portion of its surface within the interior of the meteringsection; (h) a conductor connecting the flirst electrode to the rstterminal; (i) a conductor connecting the second electrode to the secondterminal; and (j) a conductor connecting the third electrode to theother yscanning electrode; the tirst .point being separated from theother points by a distance which is a function `of the volume of thefluid suspension which is scanned during the period of an analytic runwhereby the analyzer is activated only during the period of an analyticrun and the scanning electrodes are de-energized after -an analytic run.

No references cited.

WALTER L. CARLSON, Primary Examiner.

CHARLES F. ROBERTS, Assistant Examiner.

1. A PARTICLE ANALYZER, FOR STUDYING PARTICLES SUSPENDED IN A FLUID, COMPRISING: (A) FLUID SUSPENDED PARTICLE SCANNING MEANS, HAVING A PAIR OF SCANNER ELECTRODES, FOR GENERATING SCANING SIGNALS, EACH SIGNAL HAVING A PARAMETER WHICH IS A FUNCTION OF A PHYSICAL PROPERTY OF A RESPECTIVE SCANNED PARTICLE; (B) MEANS FOR ANALYZING THE SCANNING SIGNALS; (C) LIQUID MANOMETER MEANS FOR METERING THE VOLUME OF FLUID SCANNED, HAVING A METERING SECTION; (D) MEANS FOR SENSING THE PASSAGE OF TEH MANOMETER LIQUID PAST A FIRST POINT IN THE METERING SECTION AND FOR GENERATING A FIRST PROGRAM SIGNAL; (E) MEANS FOR SENSING THE PASSAGE OF THE MANOMETER LIQUID PAST A SECOND POINT IN THE METERING SECTION AND FOR GENERATING A SECOND PROGRAM SIGNAL; (F) MEANS FOR SENSING THE PASSAGE FO THE MANOMETER LIQUID PAST A THIRD POINT IN THE METERING SECTION AND FOR GENERATING A THIRD PROGRAM SIGNAL; 